Italian researcher discovered that Gmail shutdown after sending a Zalgo text

Researchers at security firm We Are Segment have discovered a vulnerability in Gmail, a “distorted” message shuts down the most famous webmail in the world.

This Cybersec company We Are Segment, part of the Interlogica group, discovered a severe vulnerability in Gmail.

Last month the Italian firm made the headlines due to the discovery of the Tormoil vulnerability.

The flaw in Gmail was discovered by the white hat hacker Roberto Bindi, the flaw could be exploited to shut down Gmail by sending to the victim a specially crafted message, impeding the user from accessing his/her email address.

“The test was born out of curiosity. Roberto wanted to see what would have happened if a Zalgo text was injected into a web browser.” reads the press release published by the company.

A Zalgo text is a type of text composed of characters and metacharacters (letters, numbers and other symbols) which extend sideways – above and under – the original text, thanks to the effect produced by the standard Unicode combiners.

The first experiment conducted by the expert demonstrated that the insertion of a Zalgo text (which can also be generated by web applications) containing a great number of metacharacters (more than 1.000.000) triggered the browser crash, namely, the web browser shut down for a few minutes. 

Despite the already interesting results, Roberto Bindi didn’t stop there, he decided to send a Zalgo text via Gmail again, expecting another browser crash. Unfortunately, he couldn’t even imagine what kind of results this test would reveal.

What he managed to discover surpassed his imagination: it wasn’t the browser crashing; instead, it was Gmail itself.
The email is effectively received by the recipient, but he cannot open it and, after just a few moments, Gmail shuts down showing the “Error 500” message (internal server failure due to unspecified reasons, like an irreversible code error).

The young researcher managed to find a technical artifice to bypass the block and reactivate the email account, in order to repeat the experiment and verify the duration of the Gmail shutdown. He discovered that the account went down for 4 entire days.

Since this discovery, Roberto decided to contact the Google’s team. After a few weeks, the team communicated that they had begun working on the issue.

“After discovering that by sending a series of special characters the Google’s mail system stopped working, I started worrying about the possible consequences and damages that this vulnerability might have caused when publicized. An ill-intentioned person might have blocked email accounts like “purchases@…” or other work emails, by sending a simple email.” explained Roberto Bindi.
“That’s why my company decided to publish this piece of information only after the issue had been solved by Google. Our choice was based on ethics and it mirrors our company’s ethics code, underlining how WeAreSegment is formed by ethical
hackers”

This Gmail vulnerability discovered by the researcher Roberto Bindi demonstrates how research is one of the most important aspects of cyber security.

“Thanks to this activity, we can directly contribute to the Cyber Security improvement worldwide” – says Filippo Cavallarin, We Are Segment CEO.

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Pierluigi Paganini

(Security Affairs –  Gmail, hacking)

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